An abandoned castle is the site of hundreds of horrific murders perpetrated by the mysterious countess who once lived there. She's alleged to be one of the most prolific killers in history. New discoveries reveal what happened here.

A massive, alien-like fortress built into a mountainside is the central node to a network of pipelines that race outwards like tentacles; behind-the-scenes access reveals the secrets of why this strange complex was built and why it was abandoned.